1. FIELD OF THE INVENTION
This invention relates to a process for yttrium and rare earth compound catalyzed polymerization of lactones. Also provided are the living polymer compositions of such polymerizations, novel polyester products of such polymerizations and novel yttrium and rare earth metal compounds useful as catalysts in the polymerization. The resulting polymers are used in biodegradable polymers for medical uses and flexible films for packaging.
2. BACKGROUND ART
A. Hamitou, R. Jerome, and P. H. Teyssie, Journal of Polymer Science, Polymer Chemistry Edition, Vol. 15, 1035-1041 (1977) disclose the use of -oxoalkoxides of the following formula EQU (RO).sub.p-1 M.sub.2.sup.p OM.sub.1.sup.II OM.sub.2.sup.p (OR).sub.p-1
wherein M.sub.1.sup.II is Zn, Co, Mo, Fe, Cr, and Mn; M.sub.2.sup.p is Al(III) and Ti(IV) and R is any n-, sec- or tert-alkoxy group as highly active catalysts for ring opening lactone polymerization. This fast and living ring opening polymerization of lactones by these catalysts in homogeneous organic media has led to successful block copolymerization.
X. D. Feng, C. X. Song, and W. Y. Chen, Journal of Polymer Science, Polymer Letters Edition, Vol. 21, 593-600 (1983) used [(n-C.sub.4 H.sub.9 O).sub.2 AlO].sub.2 Zn, a catalyst used by Hamitou et al., above, to polymerize .epsilon.-caprolactone and R,S-lactide, either to form homopolymers or block copolymers of these monomers. The polymers are reported to have n-butoxy end groups.
H. R. Kricheldorf, M. Merl and N. Schrnagl, Macromolecules, Vol. 21 (1988), pp. 286-293 used alkoxides of Al, Ti, Zr and Sn to polymerize lactide and .epsilon.-caprolactone, and reported such polymerizations to be living. The polymer hydrocarbyloxy end groups, which originated as part of the metal hydrocarbyloxide initiator, are identified and quantitated in this paper.
A commercial literature booklet, "TONE" Polymers, Union Carbide Corp., 1988, p. 1 discloses that the polylactone polymers "TONE" P-300 and P-700 have the end group HOR--O--[--C(.dbd.O) . . . where R is an alkylene group.
JP 46/40708 [71/40708] discloses a process whereby yttrium ethoxide or yttrium 8-hydroxyquinolate catalyze the polycondensation of dimethyl terephthalate with ethylene glycol at 180.degree.-210.degree. and at 280.degree. at 0.2 mm pressure to give colorless poly(ethylene terephthalate).
U.S. Pat. Nos. 4,719,246, 4,766,182 and 4,800,219 describe the preparation, properties, and uses of a polylactide "stereocomplex" which contains interlocked segments of poly(S-lactide) and poly(R-lactide) prepared from one polymer that contains segments of poly(S-lactide) and another polymer which contains segments of poly(R-lactide).
A review of rare earth chemistry is found in R. C. Mehrotra, P. N. Kapoor and J. M. Batwara, Coordination Chemistry Reviews, Vol. 31 (1980), pp. 67-91.
Methods for the preparation of yttrium, dysprosium and ytterbium alkoxides are found in K. S. Mazdiyasni, C. T. Lynch and J. S. Smith, Inorganic Chemistry, Vol. 5 (1966), pp. 312-316.